Members of Parliament (MPs) request policy evaluations and use the resultant findings to inform law-making and hold the government to account. Since most elected representatives have developed strong ties to interest groups, one might wonder whether these privileged relationships influence MPs' parliamentary behavior. This study investigates how MPs' affiliations to groups affects their demand for policy evaluations. Empirical evidence shows that, regardless of respective party or individual characteristics, MPs are more likely to request evaluations in those policy domains where they have a group affiliation. This effect holds even when controlling for a classical measure of MP policy specialization, such as legislative committee membership. These findings suggest that ties between MPs and specific types of interest group should be considered when explaining parliamentary behavior across different policy domains.